This present invention relates in general to protection of integrated circuit chips, and more particularly, to a micromachined suppression device for protecting integrated circuit chips from electrostatic discharges or other potentially damaging voltage transients occurring during device fabrication and in use in field.
Electrostatic discharge (ESD) is a phenomenon known to degrade or destroy electronic components. In particular, given the decreasing size of circuit features with ever improving process technology, static electricity can destroy or substantially harm many of today's integrated circuits. Electrostatic discharge can occur, for example, from human handling, automated circuit testing or as a packaged circuit slides on its pins across another surface. The circuits most susceptible to damage are unpackaged or packaged finished circuits which have not yet been installed into a finished product. Once installed, for example, onto a circuit card, other means exist to protect the circuits from damage.
Various techniques have been employed to protect integrated circuit chips handled by humans during the fabrication process. These methods include special handling procedures, use of grounding equipment and the addition of protective components to the chip circuitry. The most popular technique used to protect complementary metal-oxide semiconductor (CMOS) circuits from an ESD event is the addition of diffused or implanted dual clamping diodes to clamp input and output voltages to within the boundaries of the chip's power supply connections. Such dual diodes are coupled between the input/output pads of the circuit and the pins to which the power supplies are connected. With an electrostatic discharge event of one polarity, a first diode is forward biased and with a discharge event of the opposite polarity, the second diode is forward biased. Other methods used for protecting CMOS circuits from electrostatic discharge damage are typically variations on this dual diode clamping approach. A variety of technologies are used for ESD protection both on-chip and off-chip. However, the incumbent technologies have limitations.
Furthermore, while most circuit protection needs for portable and wireless devices can be met with discrete devices, space and higher-volume manufacturing are also dictating use of integrated passive devices.
Thus, it is desirable to improve ESD suppression devices.